1. Technical Field
The present invention generally relates to suspension systems for motor vehicles. More particularly, the present invention relates to a motor vehicle suspension system including an arcuate torsion member.
2. Discussion
Conventional motor vehicles are provided with independent suspension systems for absorbing impulsive forces generated by the contact of the wheels with irregular road surfaces and other vibrations while providing a smooth and comfortable ride for the vehicle occupants. In suspension systems of this type, a torsion bar assembly is often used to increase the roll rigidity and improve the steering stability of the vehicle. As shown in the prior art arrangement illustrated in FIG. 1, typical torsion bar assemblies A include a rod-shaped member having an elongated central segment B oriented to extend laterally across the vehicle and a pair of trailing arm segments C extending longitudinally at each end of the central segment B. The central segment B of the torsion bar assembly A is supported for rotation about its axis by one or more mounting brackets D which are affixed to a vehicle body or frame E. The distal end of each trailing arm segment C is operatively coupled to one of the vehicle wheels F for vertical movement therewith.
When the vehicle is subjected to a lateral rolling force as, for example, while the vehicle negotiates a tum, the trailing arm segments C pivot in opposite directions with respect to the axis of the central segment B. As a result, torsional reaction forces are generated which act through the trailing arm segments C to urge the wheels F to move toward their normal positions. Thus, the vehicle will be prevented from excessive rolling or leaning to either side by the torsional resistance produced by the torsion bar assembly A.
One known vehicle suspension system incorporating a torsion bar is shown and described in detail in commonly assigned U.S. Pat. No. 4,637,628. The '628 patent is specifically directed to an anti-roll torsion bar arrangement for a vehicle rear suspension. A rear axle beam assembly for the suspension system includes a tubular member extending transversely between the vehicle's rear wheels. A pair of first and second outer sleeves, each fixed to the rearward end of a trailing arm, co-eccentrically surround the respective outboard end portions of the tubular member. The first sleeve is fixedly attached to one end portion of the tubular member while the second sleeve is journally mounted on the other end portion of the tubular member. A pair of first and second wheel support castings each having a collar portion defining an axially bore fixedly receiving therein the outer end of an associated outer sleeve. An anti-roll torsion bore is axially positioned in the journalled second sleeve end portion of the tubular member. The torsion bar includes a head plate on its outboard end fastened to its associated second casting with the bar's inboard end pinned to the tubular member, thereby maintaining the dimensional relationship between the left and right castings. The tubular member other end portion may rotate relative to the second sleeve upon opposite pivotal movement of the trailing arms, thereby twisting the torsion bar and increasing the roll stiffness of the suspension system. U.S. Pat. No. 4,637,628 is hereby incorporated by reference as if fully set forth herein.
Conventional torsion bars, such as the one described in U.S. Pat. No. 4,637,628, operate to convert vertical motion of the vehicle wheel and associated linkage into torsion through a moment arm in bending. To be efficient, the attachment of a torsion bar of a convention torsion bar assembly to the control arm assembly must be spaced apart as far as possible from the rotational axis of the longitudinally extending member (e.g., trailing arm or control arm) so as to obtain maximum vertical deflection (e.g., applied moment). This requirement often imposes packaging restrictions. Thus, it is desirable to provide a torsion member for a motor vehicle suspension system which reduces packaging restrictions and improves operational efficiency.